How can I know which files a proccess is accessing?

[Eduardo Meyer]

On 6/6/06, David Wolfskill <david at catwhisker.org> wrote:
> You may find the "lsof" port useful for answering such questions.
>

I tried it, but it seems that I found some limitations:

lsof: no local file space at PID 16543

# ps 16543
  PID  TT  STAT      TIME COMMAND
16543  ??  S      0:02.43 /usr/local/sbin/httpd -k start -DSSL

Any tuning would do the job?